organic compounds
Table 1
Selected torsion angles (ꢀ) for compounds (I), (II) and (III).
In view of the NÐHÁ Á Áꢀ(arene) interaction found in (I), we
have reviewed the supramolecular structures of other substi-
tuted 2-amino-6-benzyloxy-5-nitrosopyrimidines (Quesada et
al., 2002), and we have now, indeed, identi®ed NÐ
HÁ Á Áꢀ(arene) interactions in three such compounds, (V)±
(VII) (Figs. 3±5). In compound (V) (Fig. 3), the amino groups
in both independent molecules participate in exactly the same
type of asymmetric three-centre NÐHÁ Á Á(N,O) hydrogen
bond as found in (I), together with an NÐHÁ Á Áꢀ(arene)
interaction with the centroids Cg1 and Cg2 of the adjacent
(I)
3.0 (4)
177.1 (3)
179.9 (3)
4.9 (4)
(II)
(III)
1.7 (2)
81.6 (2)
62.1 (2)
1.9 (2)
N1ÐC6ÐO6ÐC67
C6ÐO6ÐC67ÐC61
O6ÐC67ÐC61ÐC62
N3ÐC4ÐO4ÐC47
C4ÐO4ÐC47ÐC41
O4ÐC47ÐC41ÐC42
178.4 (2)
179.2 (2)
6.9 (2)
2.4 (2)
176.0 (2)
23.7 (2)
176.4 (3)
92.6 (4)
179.6 (2)
11.8 (2)
ii
Ê
benzyl rings on O6 [for type 1 molecules, HÁ Á ÁCg1 2.61 A,
Table 2
Ê
Selected bond lengths (A) for (I).
ii
NÁ Á ÁCg1ii 3.418 (2) A and NÐHÁ Á ÁCg1 153ꢀ; for type 2
Ê
molecules, HÁ Á ÁCg2iii 2.50 A, NÁ Á ÁCg2 3.318 (2) A and NÐ
iii
Ê
Ê
1 1
C6ÐN1
N1ÐC2
C2ÐN3
N3ÐC4
C4ÐC5
C5ÐC6
1.306 (4)
1.347 (4)
1.353 (4)
1.310 (4)
1.408 (4)
1.419 (4)
C2ÐN2
C4ÐO4
C6ÐO6
C5ÐN5
N5ÐO5
1.316 (4)
1.342 (3)
1.334 (4)
1.374 (4)
1.245 (3)
HÁ Á ÁCg2iii 156ꢀ; symmetry codes: (ii)
x, y
,
2 2
z; (iii)
3
2
x, 12 + y,
In the P21 polymorph (Quesada et al., 2002) of compound
z].
5
2
1
2
(VI) (Fig. 4), while the hard intermolecular hydrogen bonds
formed by each of the two independent molecules are of the
two-centre NÐHÁ Á ÁN type, there are again NÐHÁ Á Áꢀ(arene)
interactions with the ring centroids, Cg3 and Cg4, of the
adjacent benzyl groups [for type 1 molecules, HÁ Á ÁCg3iv
Table 3
Hydrogen-bonding geometry (A, ) for (I).
ꢀ
Ê
iv
iv
2.79 A, NÁ Á ÁCg3 3.621 (4) A and NÐHÁ Á ÁCg3 158ꢀ; for
Cg2 is the centroid of the C41±C46 ring.
Ê
Ê
v
v
Ê
Ê
type 2 molecules, HÁ Á ÁCg4 2.68 A, NÁ Á ÁCg4 3.546 (4) A and
NÐHÁ Á ÁCg4v 170ꢀ; symmetry codes: (iv) 1 + x, y, z; (v) x 1,
y, z].
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
N2ÐH2AÁ Á ÁO4i
N2ÐH2AÁ Á ÁN5i
N2ÐH2BÁ Á ÁCg2i
0.86
0.86
0.86
2.54
2.19
2.67
2.977 (4)
3.041 (4)
3.496 (4)
112
168
163
Compound (VII), where Z0 = 1, exhibits the same type of
asymmetric three-centre NÐHÁ Á Á(N,O) hydrogen bonds as
found in both (I) and (V), but here the corresponding NÐ
HÁ Á ÁCg5 contact (Fig. 5) is long, although still close to linear
Symmetry code: (i) x; y 1; z.
iv
iv
[HÁ Á ÁCg5iv 2.91 A, NÁ Á ÁCg5 3.748 (3) A and NÐHÁ Á ÁCg5
Data collection
Ê
Ê
161ꢀ; symmetry code: (iv) 1 + x, y, z].
Nonius KappaCCD area-detector
diffractometer
' scans, and ! scans with ꢅ offsets
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski &
Minor, 1997)
3895 independent re¯ections
1203 re¯ections with I > 2ꢆ(I)
Rint = 0.014
In all of these examples, the multiple intermolecular
contacts appear to be mutually co-operative. However, it is
clear that the distinction between genuine attractive interac-
tions and adventitious contacts, or near contacts, is not easy to
judge. Nonetheless, the conformation of the benzyloxy group
involved in each such putative interaction, which effectively
prevents access of any other acceptor to the NH bond in
question, is suggestive.
ꢃmax = 27.6ꢀ
h = 14 ! 12
k = 8 ! 9
Tmin = 0.975, Tmax = 0.993
13 067 measured re¯ections
l = 25 ! 29
Re®nement
Re®nement on F2
R[F2 > 2ꢆ(F2)] = 0.063
wR(F2) = 0.169
S = 0.90
3895 re¯ections
226 parameters
H-atom parameters constrained
w = 1/[ꢆ2(Fo2) + (0.0536P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢆ)max < 0.001
3
Ê
Áꢇmax = 0.14 e A
Experimental
3
Ê
0.19 e A
Áꢇmin
=
A sample of (I) was synthesized following the published methods of
Quesada et al. (2000) and Marchal et al. (2002). Compound (IV)
(purchased from Aldrich) was converted to (II) by reaction with
sodium benzylate in toluene, and (II) was then nitrosated with
isoamyl nitrite in dimethyl sulfoxide solution at room temperature.
Crystals of (I) for single-crystal X-ray diffraction were grown by slow
evaporation of a solution in acetone.
Compound (I) crystallized in the monoclinic system; space group
P21/c was uniquely assigned from the systematic absences. H atoms
Ê
were treated as riding atoms, with CÐH = 0.93±0.97 A and NÐH =
Ê
0.86 A. The data were collected at 298 (2) K, where the proportion of
data labelled observed is only 0.31, because all attempts to cool the
crystals caused irreversible damage; this may underlie the high Rint
value and the comparatively low precision in the re®ned structure.
Data collection: KappaCCD Server Software (Nonius, 1997); cell
re®nement: DENZO±SMN (Otwinowski & Minor, 1997); data
reduction: DENZO±SMN; program(s) used to solve structure:
SHELXS97 (Sheldrick, 1997); program(s) used to re®ne structure:
SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek,
2002); software used to prepare material for publication: SHELXL97
and PRPKAPPA (Ferguson, 1999).
Crystal data
3
C18H16N4O3
Mr = 336.35
Monoclinic, P21=c
Ê
a = 11.0731 (5) A
Dx = 1.285 Mg m
Mo Kꢂ radiation
Cell parameters from 3895
re¯ections
Ê
b = 7.3642 (3) A
ꢃ = 2.9±27.6ꢀ
ꢄ = 0.09 mm
T = 298 (2) K
1
Ê
c = 22.9129 (11) A
ꢁ = 111.456 (2)ꢀ
V = 1738.94 (13) A
Z = 4
3
Ê
Needle, blue
0.25 Â 0.10 Â 0.08 mm
ꢁ
Acta Cryst. (2002). C58, o355±o358
Antonio Quesada et al. C18H16N4O3 o357